<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			var num1 = prompt("num1:")
			var num2 = prompt("num2:")
			//+两边只要有一个是字符串，就变成字符串连接符
			//+在js中有两个意思：1.字符串连接符2.算术的加号
//			alert(num1+num2)
			alert(Number(num1)+Number(num2))
			alert(typeof num1)
			//查看数据类型typeof+变量名
		</script>
	</body>
</html>
